Process of forming lens-blanks



H. K.' PARSONS.

' PROCESS OF FORMING'LENS BLANKS.

APPLICATION FILED MAR. 1h 1920.

. 1 370 042 Patented Mar. 1, 1921..

INVENTOR HAROLD K- PARSONS ATTORNEYS UNITED STATES PATENT OFFICE.

PROCESS OF FORMING LENS-BLANKS.

Specification of Letters Patent.

Patented Mar. 1, 1921.

Application filed March 11, 1920. Serial No. 364,977.

To all whom it may concern:

Be it known that I, HAROLD K. PARSONS, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Processes of Forming Lens-Blanks, of which the following is a specification.

This invention relates to improvements in lenses and has particular reference to what is commonly termed a bifocal lens.

The leadlng object of the present invention is the provision of a novel and improved process of economically constructing two part bifocal lenses.

Prior to the present invention it has been customary to form two part bifocal lenses by first grindin a countersink in an individual lens blan and then suitably mounting within this countersink a segment of different index of refraction which may be suitably secured in position'either by cementing, by fusion, or the like, after which the blank is ground to the desired prescription curve. This process has hitherto always been an individual one, but a single lens at a time being produced, and requirin the careful grinding of small segments and the like in order that the desired results might be attained.

It is, therefore, one of the principal objects of the present invention to rovide an improved process in which a p urality of lenses in place of a sin le lens may be simultaneously formed wit a single fusing or securing operation, in which larger segments easier of grinding may be employed, and in which larger segment portions will be present in the finished lens than has been possible with the method of construction in use prior to the present invention.

With these and other objects in view, therefore, my invention resides in the novel features and steps hereinafter disclosed, and it will be understood that I may make any modifications in the specific details referred" to within the scope of the appended claims without departing from or exceeding the spirit of my invention.

Figure I represents a plan view illustrating the relationship of the parts at the completion of the uniting step in my improved process.

Flg. II illustrates in a semi-diagrammatic manner one of the primary steps in my process. I D Fig. III represents an intermediate step 1n the process.

Flg. IV illustrates the splitting of the blank subsequent to uniting of the main and se ment portions.

1g. V is a sectional view illustrating the subsequent grinding of the blank in the production of the semi-finished lens.

Fig. VI represents a plan view of the blank shown in Fig. V. r

Fig. VII represents a plan view illustrating the construction of three lenses at a time in place of two.

In the drawings, where I have illustrated the-more important steps in the carrying out of my improved process, the numeral 1 designates the major portion of the blanks, having formed therein as at-2 countersinks to receive the segments 3. Prior to my invention this segment has been in the form of a hollow recess ground in the individual blank. In the carrying out of my improved process, however, I mount in juxtaposition a plurality of blanks shown in Fig. I as two, and in Fig. VII as three, blanks having their edges disposed adjacent each other but arranged in tilted relation. While supported in this position, as by the block 4, they are subjected to a simultaneous abrading action of the grinding lap or tool 5 suitably actuated as b the eccentric 6 and link 7 to swing about t e adjustable center point 8, whose position may be varied to dispose it at the radial center of whatever curve is being ground into the countersink, t h1s pivot center being mounted on the vertlcal slide 9 so that the upper spindle and rlnding tool may move downward as the g ass 1s ground away with the radius center b61115 maintained so that the curve produce while preferably being the counterpart of complementary to the curvatureon the tool is controlled by the center point on wh1ch the tool arm swings so that the tool is alor g . blanks, which curve on account of the tilting of the blanks will be deepest into the blank substantially at the geometrical center of the countersink in each blank and will cut but slightly into the inner edge of the blank to but. slightly reduce the blank thickness at that point.

This operation having been completed, the blanks are again supported in substantially the same relationship as previously upon the supporting block 4, when the segment 3 is secured in position either by cementing or fusion or the like. After this operation has been completed the segment is split as on the line IVIV'of Fig. III, for example, to provide the pair of blanks as illustrated cross-sectionally in Fig. IV, each blank having a semi-circular or sector shape segment portion 3 to one side of its major portion, the segment, however, having its thickest portion at the edge, as will be seen by reference to Fig. IV.

he blank having been prepared to this extent, I then form or have formed subsequently on the segment face the prescription curve 12 shown in full lines in Fig. V, which is so ground as to remove the projecting portion 13 of the segment shown in dotted lines and to produce a final finished lens surface substantially as "indicated by said full lines 12 appearin in lanes illustrated in connection-with 1g. of the present drawings, the final lens being suitably cut out from the blank in question, as shown by the dotted lines in Fig. VI'illustrating the cutting of a large round eye. lens from one-of the blanks in question. i

It will be fiderstood that the varioussteps in the process and results obtained are substantially identical when the three blank form shown in Fig. VII is made use of in place of the two blank form particularly described.

-It is to be understood that the segment 3 is in all ordinary cases of a glass of higher index of refraction than the major blank 1 in order that a difference in focal value of the two portions may be obtained throu h this difference in index of refraction of the glasses, although in some instances it may be of glass of a lower index of refraction as when the central portion is to be used for distant and the upper portion for near vision work, or it may even be of a of the glass of the same index of refraction but having difl'erent properties, as when protection from ultra violet or other rays is desired for a particular kind of work.

I claim:

1. The process of forming bifocal lens blankis consisting in supporting a plurality of blanks in tilted relation, simultaneously centrally abrading the composite blank thus formed, supporting the relationship occupied durin the grinding operation and simultaneous y securing a single segment within the recesses of the several blanks.

2. The process of forming bifocal lens blanks consisting in supporting a plurality of blanks in tilted relation, simultaneously centrally abrading the composite blank thus formed, supporting the relationship occupied during the grinding operation, simultaneously securing a single segment within the recesses of the several blanks, and splitting the segment, to provide a portion for each individual blank.

3. The process of forming bifocal lens blanks consisting in supporting a plurality of blanks in tilted relation, simultaneously centrally abrading the composite blank thus formed, supporting the relationship occupied during the grinding operation, simultaneously securing a sin le segment withm the recesses of the severa blanks, splitting the segment to provide aportion for each individual blank, and grinding the segment bearing face of the blank to remove the excess edge thickness of the segment.

4. The rocess of formmg lens blanks including orming countersinks in a plurality of blanks, supporting the blanks in relatively tilted relation with their countersinks in juxtaposition, forming a button to fit said countersinks, securing the button within the countersinks, and subsequently splitting the button to provide an individual section remaining with each original blank.

5. The process of forming bifocal lenses consisting in supporting a plurality of blanks in tilted relation with their edges in juxtaposition, simultaneously grinding the adjacent portions of the several blanks,

maintaining the blanks in tilted relation, and simultaneously filling the countersinks formed by grinding with a portion of glass of a different index of refraction.

6. The process of forming bifocal lenses consisting in supporting a plurality of blanks in tilted relation with their edges in juxtaposition, simultaneously grinding the adjacent portions of the several lanks,main1- taining the blanks in tilted relation, simultaneously filling the countersinks formed by grinding with a portion of glass of a different index of refraction, and subsequently separating the blanks and filler.

7 The process of forming bifocal lenses consisting in supporting a plurality of blanks in tilted relation with their edges in individual blanks after separation to remove juxtaposition, simultaneously grinding the the central excess portion of the filler. 10 adjacent portions of the several blanks, In testimony whereof I have aflixed my maintaining the blanks in tilted relation, sisignature, in presence "of two Witnesses. 1

5 multaneously filling the countersinks formed 1 HAROLD K. PARSONS. by grinding with a portion of glass of a dif- Witnesses: ferent index of refraction subsequently sepa- ESTHER M. LAFLER, I rating the blanks and filler, and grinding the I ALICE G. HASKELL. 

